The lrucache package

This package contains a simple, pure LRU cache, implemented in
terms of Data.Map.

It also contains a mutable IO wrapper providing atomic updates to
an LRU cache.

Version History:

1.0 - Breaking API changes:
1) The newLRU smart constructor now makes the maximum
size optional.
2) The delete function now returns the value removed, if
one was.
Additionally, a function was added to remove the least-recently
used element in the LRU.